bug#38187: 27.0.50; No mouse-wheel scaling on images

[Juri Linkov]

>> I noticed that using the mouse-wheel on images is not responsive enough.
>> It takes too much time when every step of the mouse scrolling wheel
>> needs to scale the image separately for every consecutive rescaling.
>
> Yeah, users are more likely to issue a bunch of scroll wheel events
> rapidly than hitting `+' at the same rate, I guess.
>
>> So I experimented with debouncing - a new macro 'debounce' swallows
>> all intermediate calls in quick succession to 'image--change-size',
>> and executes only the last call in sequence.
>>
>> But actually it requires another better macro 'debounce-reduce'
>> that accumulates the state from all calls by multiplying all
>> intermediate scaling factors, and using the result on the final call:
>
> Makes sense to me.

This is installed now.

Not sure if this report can be closed, since the discussion
on image memory caching moved to bug#38345.